Returning array key randomized based on probabilities in php

Question

I am trying to make predictions with an exported random forest model in php. I have a code that imports all the individual trees in the forest, makes predictions with each tree and chooses the outcome with most votes.

Instead, I want the code to return a randomized outcome taking into account the number of votes (i.e. probability of the outcomes). Any ideas how I can go about this?

Here is the code I currently have. I want to modify the 'evaluate' function at the end.

/* Class for individual tree branches */

    class branch
    {
        public $split_var;
        public $status;
        public $prediction;

        private $left;
        private $right;
        private $split_point;

        public function __construct($line) {
            $this -> left = $line[1] - 1; /* Because R output is 1-indexed, not 0-indexed */
            $this -> right = $line[2] - 1;
            $this -> split_var = $line[3] - 1;
            $this -> split_point = $line[4];
            $this -> status = $line[5];
            $this -> prediction = $line[6];
        }

        public function get_next($value) {
            if ($value <= $this -> split_point) return($this -> left);
            else return($this -> right);
        }
    }

    /* Class for the trees themselves */

    class tree
    {
        private $branches = array();

        public function add_branch($line) {
            $this -> branches[] = new branch($line);
        }

        public function evaluate($data)
        {
            $decision = null;
            $current_branch = 0;

            while ($decision === null)
            {
                if ($this -> branches[$current_branch] -> status == -1) $decision = $this -> branches[$current_branch] -> prediction;
                else $current_branch = $this -> branches[$current_branch] -> get_next($data[$this -> branches[$current_branch] -> split_var]);
            }

            return($decision);
        }
    }
    /* And for the forest */

    class forest
    {
        private $trees = array();

        public function __construct($file_loc)
        {
            $model_file = fopen($file_loc, 'r');
            fgetcsv($model_file); /* Discard the header */

            $current_tree_index = -1;

            while (($line = fgetcsv($model_file)) !== false)
            {
                if ($line[0] - 1 > $current_tree_index) /* Again, adjusting for R output being 1-indexed */
                {
                    $this -> trees[] = new tree;
                    $current_tree_index ++;
                }
                $this -> trees[$current_tree_index] -> add_branch($line);
            }

            fclose($model_file);
        }

        public function evaluate($data)
        {
            $votes = array();

            foreach($this -> trees as $current)
            {
                $current_vote = $current -> evaluate($data);

                if (! array_key_exists($current_vote, $votes)) $votes[$current_vote] = 0;
                $votes[$current_vote] ++;
            }

            return(array_keys($votes, max($votes))[0]);
        }
    }